Buggy code:
public class ItemMetaUtil { public static String getNameString ( final ItemStack is ) { } public static String getLoreString ( final ItemStack is ) { } public static String getSpecialMetaString ( final ItemStack is , final String [ ] separators ) throws InventoryUtilException { } public static ItemMeta fromString ( final ItemMeta meta , final String nameString , final String loreString , final String specialMetaString , final String [ ] separators ) throws InventoryUtilException { } public static void saveToConfigSection ( final ConfigurationSection itemSection , final ItemStack is ) { } private static ConfigurationSection createAndGetSection ( final ConfigurationSection parent , final String key ) { } public static void loadFromConfigSection ( final ConfigurationSection itemSection , final ItemStack is ) throws InventoryUtilException { } private static String getBookMetaString ( final BookMeta meta ) { } private static void parseBookMetaString ( final String string , final BookMeta meta ) { } private static void saveBookMetaToConfigSection ( final ConfigurationSection metaSection , final BookMeta meta ) { } private static void loadBookMetaFromConfigSection ( final ConfigurationSection metaSection , final BookMeta meta ) { } private static String getEnchantmentStorageMetaString ( final EnchantmentStorageMeta meta , final String [ ] separators ) { } private static void parseEnchantmentStorageMetaString ( final String string , final EnchantmentStorageMeta meta , final String [ ] separators ) throws InventoryUtilException { } private static void saveEnchantmentStorageMetaToConfigSection ( final ConfigurationSection metaSection , final EnchantmentStorageMeta meta ) { } private static void loadEnchantmentStorageMetaFromConfigSection ( final ConfigurationSection metaSection , final EnchantmentStorageMeta meta ) throws InventoryUtilException { } private static String getFireworkEffectMetaString ( final FireworkEffectMeta meta ) { } private static String getFireworkEffectString ( final FireworkEffect effect ) { } private static void parseFireworkEffectMetaString ( final String string , final FireworkEffectMeta meta ) { } private static FireworkEffect parseFireworkEffectString ( final String string ) { } private static void saveFireworkEffectMetaToConfigSection ( final ConfigurationSection metaSection , final FireworkEffectMeta meta ) { } private static void saveFireworkEffectMetaToConfigSection ( final ConfigurationSection metaSection , final FireworkEffectMeta meta , final String sectionName ) { } private static void saveFireworkEffectToConfigSection ( final ConfigurationSection metaSection , final FireworkEffect effect , final String sectionName ) { } private static void loadFireworkEffectMetaFromConfigSection ( final ConfigurationSection metaSection , final FireworkEffectMeta meta ) { } private static void loadFireworkEffectMetaFromConfigSection ( final ConfigurationSection metaSection , final FireworkEffectMeta meta , final String sectionName ) { } private static FireworkEffect loadFireworkEffectFromConfigSection ( final ConfigurationSection metaSection , final String sectionName ) { } private static String getFireworkMetaString ( final FireworkMeta meta , final String [ ] separators ) { } private static void parseFireworkMetaString ( final String string , final FireworkMeta meta , final String [ ] separators ) { } private static void saveFireworkMetaToConfigSection ( final ConfigurationSection metaSection , final FireworkMeta meta ) { } private static void loadFireworkMetaFromConfigSection ( final ConfigurationSection metaSection , final FireworkMeta meta ) { } private static String getLeatherArmorMetaString ( final LeatherArmorMeta meta ) { } private static void parseLeatherArmorMetaString ( final String string , final LeatherArmorMeta meta ) { } private static void saveLeatherArmorMetaToConfigSection ( final ConfigurationSection metaSection , final LeatherArmorMeta meta ) { } private static void loadLeatherArmorMetaFromConfigSection ( final ConfigurationSection metaSection , final LeatherArmorMeta meta ) { } private static String getMapMetaString ( final MapMeta meta ) { } private static void parseMapMetaString ( final String string , final MapMeta meta ) { } private static void saveMapMetaToConfigSection ( final ConfigurationSection metaSection , final MapMeta meta ) { } private static void loadMapMetaFromConfigSection ( final ConfigurationSection metaSection , final MapMeta meta ) { } private static String getPotionMetaString ( final PotionMeta meta , final String [ ] separators ) { } private static void parsePotionMetaString ( final String string , final PotionMeta meta , final String [ ] separators ) { } private static void savePotionMetaToConfigSection ( final ConfigurationSection metaSection , final PotionMeta meta ) { } private static void loadPotionMetaFromConfigSection ( final ConfigurationSection metaSection , final PotionMeta meta ) { if ( metaSection . isConfigurationSection ( "potion" ) ) { final ConfigurationSection potionSection = metaSection . getConfigurationSection ( "potion" ) ; for ( final String key : potionSection . getKeys ( false ) ) { if ( ( key . startsWith ( "potionEffect" ) ) && ( potionSection . isConfigurationSection ( key ) ) ) { <START_BUG> final ConfigurationSection potionEffectSection = metaSection . getConfigurationSection ( key ) ; <END_BUG> final PotionEffectType type = PotionEffectType . getByName ( potionEffectSection . getString ( "type" ) ) ; final int duration = potionEffectSection . getInt ( "duration" ) ; final int amplifier = potionEffectSection . getInt ( "amplifier" ) ; meta . addCustomEffect ( new org . bukkit . potion . PotionEffect ( type , duration , amplifier ) , true ) ; } } } } private static String getSkullMetaString ( final SkullMeta meta ) { } private static void parseSkullMetaString ( final String string , final SkullMeta meta ) { } private static void saveSkullMetaToConfigSection ( final ConfigurationSection metaSection , final SkullMeta meta ) { } private static void loadSkullMetaFromConfigSection ( final ConfigurationSection metaSection , final SkullMeta meta ) { } }

Fix:
final ConfigurationSection potionEffectSection = potionSection . getConfigurationSection ( key ) ;